Flat panel display devices typically include a thin, rectangular-shaped backplate and a thin, rectangular-shaped faceplate overlying the backplate. The faceplate is attached to the backplate such that a cavity is formed between the faceplate and the backplate. The cavity is a vacated to create high vacuum conditions within the cavity. In some flat panel displays, the vacuum pressure is approximately 1.times.10.sup.-7 torr. An anode plate overlies the inner surface of the faceplate and is coated with light emissive elements, such as phosphors, which define the active region of the display. The phosphors are capable of emitting either red, blue, or green light. Typically, the phosphors are arranged on an anode plate in red-blue-green triads called picture elements or pixels. In a field emission display (FED), a plurality of electron emitters are arrayed on a cathode plate overlying the inner surface of the backplate. Upon being struck by electrons emitted from the electron emitters, the phosphors are caused to emit red, blue, or green light which is seen by a viewer observing the outer surface of the faceplate.
The faceplate and the backplate of the display are constructed of relatively thin glass having a large rectangular surface area. When the display is evacuated, considerable pressure is exerted upon the exterior surfaces of the faceplate and the backplate. To prevent the faceplate and the backplate from bowing inward toward the cavity, it is common to provide a series of spacers positioned between the faceplate and the backplate. The spacers are arranged in such a way as to prevent pressure-induced distortions in the faceplate or the backplate of the display.
The spacers are typically thin, rectangular bars having a high aspect ratio (height/width) and a width of about 100 microns or more. The spacers are located within the cavity in such a way as to avoid blocking electrons generated by the electron emitters. In typical flat panel displays, the spacers are carefully aligned, such that no spacer overlies an electron emitter. Even when the spacers are precisely aligned to the emitters on the cathode plate, the spacers can disrupt the electric field within the cavity, such that the surface of the spacers attain an electrical charge. Misalignment of the spacers can result in increased charging of the spacers. When either of these events occur, a dark spot can be created on the faceplate that is visible to a viewer observing the display.
In a high-voltage FED, the separation distance between the faceplate and the backplate is on the order of 1 millimeter. Accordingly, to avoid creating a defect the spacers require an aspect ratio of about 20:1. At high voltages, major occlusion of electron emitters immediately appears as a visible dark region of the faceplate of the display. To avoid occlusion of electron emitters, methods of the prior art have included the careful alignment of the spacers to the electron emitters in order to avoid any overlap or occlusion of the emitters by the spacers within the display. The requirements for careful alignment, together with the need to fabricate spacers having a rectangular geometry similar to the arrangement of electron emitters on the backplate presents major difficulty in flat panel display fabrication. Accordingly, a need existed for an improved spacer geometry and fabricating method that permits easy placement of spacers within the display, while avoiding the creation of dark regions on the faceplate of the display.